CN104953829A - Quasi frequency peak current control method applied to BUCK circuit - Google Patents

Abstract

The invention discloses a quasi frequency peak current control method applied to a BUCK circuit. Output voltage and inductive current signals are acquired, switch on time and off time are obtained by a quasi frequency control method, switch control signals are generated, and a BUCK converter is controlled. A control system comprises a data acquisition module 01, an outer ring voltage PI (proportional-integral) controller module 02, a slope calculation module 03, an on and off time calculation module 04 and a modulation module 05. The slope of inductive current is calculated when a switch is turned on and off, the on time and the off time are calculated, the switch control signals are acquired by the modulation module, the BUCK converter is controlled, and steady and transient performances of the BUCK converter are improved by the quasi frequency control method.

Description

A kind of peak current control method certainly being frequently applied to BUCK circuit

Technical field

The present invention relates to BUCK circuit in field of switch power (comprising normal shock type, flyback and half-bridge bridge-type BUCK converter) Control System Design and the field of manufacture.

Background technology

DC-DC converter application is extensively non-, is especially all widely applied in fields such as military affairs, industry, family, medical treatment and collieries.Traditional DC-DC converting power source often adopts linear power supply technology, but this version causes, and power source integral efficiency is on the low side, performance is not good, and volume and the problem such as weight is large.Therefore, DC power supply tend to adopt switch power technology, DC power supply is become efficiency is high, performance is better, volume is little, lightweight.Along with the fast development of power electronic technology, more facilitate fast development and the innovation of switch power technology, application is also more and more extensive, and the proportion occupied by whole field of power supplies breaker in middle power supply is more and more large.

In order to promote the dynamic property of DC-DC switching power converters, output accuracy and moment current-limiting protection, occurred current ripples control technology, this technology facilitates the development that DC switch power supply converter controls significantly.This current ripples control technology is mainly divided into peak value comparison method and valley point current to control two kinds.But as duty ratio D>50%, peak value comparison method there will be the phenomenon of current inner loop instability, as duty ratio D<50%, valley point current controls the phenomenon that also there will be this instability.This will affect transient response performance and the steady state voltage precision of converter.

For solving the phenomenon of this current inner loop instability, there is harmonic compensation method.If but the compensation of all duty cycle range is carried out with same constant compensation slope, this usually causes slope compensation amount greatly superfluous, has a strong impact on the transient response characteristic of Switching Power Supply.Particularly state of a control, when output current is zero, excessive compensation also may cause peak-current mode to control to change voltage mode control into, what this neither be desired.Method based on slope compensation just requires to produce different compensation slopes under different duty, and this can increase the operand of control system and occur that some compensate the instability problem of slope switching.

Summary of the invention

In view of the above shortcoming of prior art, the object of the invention is, for BUCK converter peak value comparison method technology, provide a kind of current ripples control technology certainly being frequently applicable to DC switch power supply converter.Make it the mapping that can not only improve conventional current ripple control technology, the wild effects such as subharmonic concussion can also be eliminated, thus improve the steady-state characteristic of converter.

The present invention realizes its goal of the invention and is achieved by the following technical solution.

Be applied to a peak current control method certainly frequently for BUCK converter, gather output voltage and inductor current signal, obtain switch conduction times and turn-off time by control method certainly frequently, generate switch controlling signal, complete the control of BUCK converter; Control system is by data acquisition 01, and outer loop voltag PI controller 02, slope calculating 03, conducting and turn-off time calculate 04, modulation module 05 5 module compositions, and control flow comprises following steps:

First, in the beginning of control cycle, obtain output voltage by data acquisition module 01 and be denoted as v _{o_n}and inductive current is denoted as i _n, calculate the 03 output voltage v that will gather by slope _{o_n}calculate according to formula (1.1), obtain inductive current rate of change m ₁and m ₂;

$\left\{\begin{array}{c}{m}_1=\frac{v_g-v_{o\_n}}{L}\\ m_2=\frac{v_{o\_n}}{L}\end{array}\right.---\left(0.1\right)$

Wherein: v _gfor BUCK converter input voltage, its value stabilization; v _{o_n}for the output voltage that BUCK converter n-th switch periods gathers; L is the size of inductance value; m ₁for the climbing of inductive current after switch conduction; m ₂for switch closes the rate of descent of rear inductive current;

Meanwhile, given size of current i is calculated by outer voltage 02 _c.

Then, 04 is calculated by inductor current value i by service time and turn-off time _nand given current i _cswitch conduction times and switch OFF time is calculated respectively according to formula (1.2);

$\left\{\begin{array}{c}{i}_n\&le;i_{\mathrm{ct}}\left\{\begin{array}{c}{t}_{\mathrm{on}\_n}=\frac{i_c-i_n}{m_1}\\ t_{\mathrm{off}\_n}=\left\{\begin{array}{c}{t}_{\mathrm{off}\_\min }(t_{\mathrm{on}\_n}>t_{\mathrm{on}\_\max })\\ \frac{m_1}{m_1+m_2}{T}_{\mathrm{set}}\end{array}\right.\end{array}\right.\\ i_n>i_c\left\{\begin{array}{c}{t}_{\mathrm{on}\_n}=t_{\mathrm{on}\_\min }\\ t_{\mathrm{off}\_n}=\frac{i_n-i_c}{m_2}+\frac{m_1}{m_1+m_2}{T}_{\mathrm{set}}(t_{\mathrm{off}\_n}\&Element;[t_{\mathrm{off}\_\min },t_{\mathrm{off}\_\max }\left]\right)\end{array}\right.\end{array}\right.---\left(0.2\right)$

Wherein: t _{on_n}it is the time of the n-th switch periods switch conduction; t _{off_n}it was the n-th time of carrying out cycle switch shutoff; t _{on_min}for the minimum value of switch conduction times; t _{on_max}for the maximum of switch conduction times; t _{off_min}for the minimum value of switch OFF time; t _{off_max}for the maximum of switch OFF time; T _setfor desired switch periods;

Finally, by switch conduction times t that modulation module 05 will obtain _{on_n}with switch OFF time t _{off_n}become switch controlling signal, complete the control in a switch periods of BUCK converter.

Compared with prior art, the invention has the beneficial effects as follows:

One, control system is easy to realize, and operand is little, is easy to Digital Implementation.

Two, the dynamic response performance of system effectively can be improved relative to conventional current ripple control.

Three, the phenomenon of the current inner loop instability occurred in conventional current ripple control can effectively be eliminated, such as subharmonic concussion.

Four, there is higher universal performance, the all switching power circuits similar with BUCK converter can be applied to, not only be suitable for current ripples control technology: current peak controls and electric current valley controls, and is also suitable for voltage ripple control technology equally: voltage peak controls and voltage dips controls.

Accompanying drawing explanation

Certainly frequently, the peak value comparison method system block diagram of Figure 1B UCK circuit

Fig. 2 BUCK converter slope computing block diagram

Fig. 3 BUCK converter switches ON time and turn-off time computing block diagram.

Fig. 4 works as i _nbe less than or equal to i _ctime control waveform figure

Fig. 5 works as i _nbe greater than i _ctime control waveform figure

Fig. 6 conventional peak Current Control is switched to peak current control method certainly frequently, wherein (a) is switched to control waveform figure certainly frequently for Traditional control, b () is conventional peak Current Control stable state oscillogram, (c) is peak value comparison method stable state oscillogram certainly frequently.

Output voltage when starting under Fig. 7 conventional peak Current Control (a) and certainly frequently peak value comparison method (b) and the oscillogram of inductive current

The oscillogram of output voltage and inductive current when load reduces under Fig. 8 conventional peak Current Control (a) and certainly frequently peak value comparison method (b)

The oscillogram of output voltage and inductive current when load reduces under Fig. 9 conventional peak Current Control (a) and certainly frequently peak value comparison method (b)

Embodiment

Fig. 1 illustrates the peak current control method system block diagram certainly frequently of BUCK circuit.Whole system comprises: data acquisition 01 gathers output voltage v _oand inductive current i _l, output voltage obtains peak current set-point i through outer loop voltag PI controller 02 _c.In addition, according to output voltage v _oand the input voltage v stored _gcalculate 03 by slope and obtain inductive current climbing m ₁with inductive current rate of descent m ₂.In conjunction with peak current set-point i _cand inductive current rate of change m ₁and m ₂04 compute switch ON time t is calculated by conducting and turn-off time _onwith switch OFF time t _off.Last according to switch conduction times t _onwith switch OFF time t _offobtain the control signal of converter through modulation module 05, complete the control of converter.Wherein the particular content of main modular is:

(1) slope calculates

To the output voltage gathered, the input voltage value stored in microcontroller and inductor current value processes and computing, when completing switch conduction and switch OFF time inductive current rate of change calculating.

(2) conducting and turn-off time calculate

Inductive current rate of change, given value of current value (outer shroud voltage output value) and inductive current collection value are processed and computing, realizes the calculating of switch conduction times and turn-off time.

Fig. 2 illustrates, BUCK converter slope computing block diagram.The input voltage signal stored in output voltage signal and this locality is according to the expression formula shown in Fig. 2: utilize input voltage v _gdeduct output voltage v _{o_n}difference inductive current climbing m when switch is opened when obtaining the work of BUCK converter divided by inductance value L ₁, utilize output voltage v _{o_n}the rate of descent m of converter operating room inductive current when switch OFF is obtained divided by inductance value L ₂.

Fig. 3 illustrates, BUCK converter switches service time and turn-off time computing block diagram.The inductor current signal obtained and given current signal are compared, point inductive current sampled value i _nbe greater than outer shroud peak current set-point i _cand be less than outer shroud peak current set-point i _ctwo kinds of situation compute switch pipe ON time and turn-off time.As inductive current sampled value i _nbe less than peak current set-point i _ctime, switch service time t _{on_n}for value given value of current value i _cdeduct inductive current sampled value i _ndifference is divided by inductive current climbing m ₁, work as t _{on_n}be greater than t _{on_max}time, switch OFF time t _{off_n}for t _{off_min}, otherwise switch OFF time t _{off_n}for m ₁divided by m ₁with m ₂and be multiplied by configuration switch cycle T again _set; As inductive current sampled value i _nbe greater than peak current set-point i _ctime, switch conduction times t _{on_n}for t _{on_min}, switch OFF time t _offfor inductive current sampled value i _ndeduct peak current set-point i _cdivided by m ₂with m ₁divided by m ₁with m ₂and be multiplied by configuration switch cycle T again _setand, its amplitude limit is t _{off_max}.

When not departing from inventive concept, those skilled in the art are not when departing from scope and spirit of the present invention, and all apparent amendment about form and details carry out it or change all should drop in protection scope of the present invention.

Claims (3)

1. be applied to a peak current control method certainly frequently for BUCK circuit, gather output voltage and inductor current signal, obtain switch conduction times and turn-off time by control method certainly frequently, generate switch controlling signal, complete the control of BUCK converter; Control system is by data acquisition (01), and outer loop voltag PI controller (02), slope calculating (03), conducting and turn-off time calculate (04), modulation module (05) five module composition; Control flow comprises following steps:

First, in the beginning of control cycle, obtain output voltage by data acquisition module (01) and be denoted as v _{o_n}and inductive current is denoted as i _n, the output voltage v that will be gathered by slope calculating (03) _{o_n}calculate according to formula (1.1), obtain inductive current rate of change m ₁and m ₂;

Wherein: v _gfor BUCK converter input voltage, its value stabilization; v _{o_n}for the output voltage that BUCK converter n-th switch periods gathers; L is the size of inductance value; m ₁for the climbing of inductive current after switch conduction; m ₂for switch closes the rate of descent of rear inductive current;

Meanwhile, given size of current i is calculated by outer voltage (02) _c;

Then, (04) is calculated by inductor current value i by service time and turn-off time _nand given current i _cswitch conduction times and switch OFF time is calculated respectively according to formula (1.2);

Wherein: t _{on_n}it is the time of the n-th switch periods switch conduction; t _{off_n}it was the n-th time of carrying out cycle switch shutoff; t _{on_min}for the minimum value of switch conduction times; t _{on_max}for the maximum of switch conduction times; t _{off_min}for the minimum value of switch OFF time; t _{off_max}for the maximum of switch OFF time; T _setfor desired switch periods;

Finally, by switch conduction times t that modulation module (05) will obtain _{on_n}with switch OFF time t _{off_n}become switch controlling signal, complete the control in a switch periods of BUCK converter.

2. the peak current control method certainly being frequently applied to BUCK circuit according to claim 1, it is characterized in that, control cycle starts to gather output voltage values U _oand inductor current value i _l, gather output voltage values U _ofor calculating climbing m during inductive current switch conduction ₁and rate of descent m during switch OFF ₂, the set-point i of inductive current peak is obtained by outer shroud PI controller _c.Then according to the inductor current value i gathered _l, inductive current climbing m ₁, inductive current rate of descent m ₂and current peak set-point i _ccalculate switch conduction times t _onwith switch OFF time t _off.

3. the peak current control method certainly being frequently applied to BUCK circuit according to claim 1, it is characterized in that, modulation module obtains the control impuls of BUCK circuit according to the switch conduction times calculated and switch OFF time.